The major goal of this project is to determine the role of existing or new viruses in the etiology of AIDS. The study will prospectively follow and monitor three groups of human subjects; two groups at high risk for AIDS plus a group of AIDS patients. The three groups are (a) 240 hemophiliac patients (b) 100 young gay males in Boston (c) AIDS patients in Massachusetts General Hospital The people in these groups will be monitored for the presence of genomes of six viruses and attempts will be made to isolate genomes of new viruses. The six viruses are cytomegalovirus, Epstein-Barr virus, human T-cell leukemia virus, adenovirus type 35, lymphotropic papovavirus and Herpesvirus saimiri-like viruses. The presence of their genomes will be monitored by 1) dot-blot hybridization, 2) Southern gel hybridization, 3) restriction endonuclease analysis of virus isolated in this study and 4) Eckhardt-type gel analysis. Attempts will be made to isolate by molecular genomes of new viruses of AIDS patients from Eckhardt-type gels. This study will be performed collaboratively with two ongoing immunological studies on groups a, and b and c respectively.